1. Field of the Invention
The present invention relates to telemetry systems for use in wellbore operations. More particularly, the present invention relates to wellbore telemetry systems, such as wired drill pipe telemetry, for passing signals between a surface unit and a downhole tool positionable in a wellbore penetrating a subterranean formation.
2. Background of the Related Art
Wellbores are drilled to locate and produce hydrocarbons. A downhole drilling tool with a bit at and end thereof is advanced into the ground to form a wellbore. As the drilling tool is advanced, a drilling mud is pumped from a surface mud pit, through the drilling tool and out the drill bit to cool the drilling tool and carry away cuttings. The fluid exits the drill bit and flows back up to the surface for recirculation through the tool. The drilling mud is also used to form a mudcake to line the wellbore.
During the drilling operation, it is desirable to provide communication between the surface and the downhole tool. Wellbore telemetry devices are typically used to allow, for example, power, command and/or communication signals to pass between a surface unit and the downhole tool. These signals are used to control and/or power the operation of the downhole tool and send downhole information to the surface.
Several different types of telemetry systems have been developed to pass signals between the surface unit and the downhole tool. For example, mud pulse telemetry systems use variations in the flow of mud passing from a mud pit to a downhole tool and back to the surface to send decodable signals. Examples of such mud pulse telemetry tools may be found in U.S. Pat. Nos. 5,375,098 and 5,517,464. In addition to mud pulse wellbore telemetry systems, other wellbore telemetry systems may be used to establish the desired communication capabilities. Examples of such systems may include a drill pipe wellbore telemetry system as described in U.S. Pat. No. 6,641,434, an electromagnetic wellbore telemetry system as described in U.S. Pat. No. 5,624,051, an acoustic wellbore telemetry system as described in PCT Patent Application No. WO2004085796. Other data conveyance or communication devices, such as transceivers coupled to sensors, have also be used transmit power and/or data. Depending on the wellbore conditions, data transmission rates and/or other factors, it may be preferable to use certain types of telemetry for certain operations.
In particular, drill pipe telemetry has been used to provide a wired communication link between a surface unit and the downhole tool. The concept of routing a wire in interconnected drill pipe joints has been proposed, for example, in U.S. Pat. No. 4,126,848 by Denison; U.S. Pat. No. 3,957,118 by Barry et al.; and U.S. Pat. No. 3,807,502 by Heilhecker et al.; and in publications such as “Four Different Systems Used for MWD”, W. J. McDonald, The Oil and Gas Journal, pages 115-124, Apr. 3, 1978. A number of more recent patents and publication have focused on the use of current-coupled inductive couplers in wired drill pipe (WDP) as described, for example, in U.S. Pat. Nos. 4,605,268; 2,140,537; 5,052,941; 4,806,928; 4,901,069; 5,531,592; 5,278,550; 5,971,072; 6,866,306 and 6,641,434; Russian Federation published Patent Application No. 2040691; and PCT Application No. WO 90/14497. A number of other patent references have disclosed or suggested particular solutions for data transmission along the axial lengths of downhole conduit or pipe joints, such as U.S. Pat. Nos. 2,000,716; 2,096,359; 4,095,865; 472,402; 4,953,636; 6,392,317; 6,799,632 and US 2004/0119607; and PCT Application Nos. WO 2004/033847 and WO 0206716. Some techniques have described a wire positioned in a tube and placed inside a drill collar as shown, for example, in U.S. Pat. No. 4,126,848.
Despite these advancements in wired drill pipe telemetry technology, there remains a need to provide a reliable telemetry system. It is desirable that such a system provide techniques for protecting electrical components. It is further desirable that such a system be easily manufactured, machined and/or modified. Such a system is preferably capable of one or more of the following, among others: reduced electrical faults and/or failures, good contact between adjacent pipes, redundant components, and/or back up systems.